To define a charge distribution one begins with a statement of what hadron state is to be used. The suggestion in [1]}, here with hadron helicity \(\lambda \)  included, is equivalent to a state written as [2]}, [3]}, [1]}, [5]}
\(\mathinner {|{\Phi , \lambda }\rangle } = \mathcal {N}\int \frac{ d^3p }{ (2\pi )^3 }\frac{1}{ \sqrt{2 E_p} }\mathinner {|{\vec{p},\lambda }\rangle } \,.\) 
